The present invention relates to a method and apparatus enabling a comparatively quick segregation of petroleum products, particularly from liquid mixtures containing mostly water but also an emulsifying agent, the petroleum products and possibly also other lighter liquid components forming an emulsion together with the water and the emulsifying agent.
The presently known methods of separating emulsions in a more or less controlled way are heating, chemical break-down, centrifugal techniques, the use of ceramic filters or (most frequently) a combination of such measures. In relation to capacity, such systems are very expensive and involve high operational costs.
As opposed to these methods, the inventive method is based on the fact that emulsions containing water and petroleum break down into their components as soon as the emulsion is formed, a phenomenon referred to below as self-separation.
The basic problem to be solved by the invention is to avoid the discharge of dispersed petroleum products into draining systems ending at purifying plants. In fact, petroleum has a deleterious influence on the biological part of a purifying plant and, in pace with the development of purifying plants, more and more attention has been paid to this problem.
Emulsion containing petroleum products are extensively used particularly at industrial plants, petrol stations and motor repair shops. In order to remove oil, grease, asphalt wax, polish or similar products from vehicles, engines, polished stainless parts etc., one normally uses cleaning liquids comprising white spirit with high contents of aromatics and an emulsifying agent added thereto. After washing with water, an emulsion having a density very close to that of water is formed and consequently, such an emulsion cannot be separated in conventional oil separators. If the emulsion is discharged through an oil separator containing previously segregated oil this oil will be emulsified and follow the water through the outlet.
The authorities have also drawn their attention to this problem, and efforts are now being made to establish standards relating to such cleaning liquids forming emulsions. It has been proposed to permit only such cleaning liquids which, upon mixing with prescribed quantities of polish, lubricating oils, anti-rust agents, etc. and dilution in water into an emulsion, separate spontaneously within a prescribed time period to such an extent that the remaining contents of petroleum fall below a certain limit value, e.g. 100 ppm, which is also the maximum value to be permitted for discharge into draining systems leading to purifying plants.
The problem is, however, that hitherto no method has been found which enables the self-separation of an emulsion in large quantities and which is sufficiently simple, reliable in operation and cheap to be applicable at petrol stations, motor repair shops and minor industrial plants.